I have searched threads regarding mounting of rear lights to aero posts but this question is a little more specific to the Cygolite Hotshot. I have a Giant with the aero shaped seat post. I have a generic aero post mount, one where the reflector was attached.

The issue is, the diameter of the locking nut (around 5mm) on the mount is too large for the screw on Cygolite's little bracket (the fixing screw is around 3mm diameter). The only way to securely mount the light is to use its proprietary bracket and I need to somehow fix to the aero post mount (it only came with a round post mount and they don't make an aero one).

Does anybody have one of these lights and an aero post and if so, how did you get the Cygolite bracket to attach to your existing post mount? Anyone know of an aero post mount with a 3mm locking nut diameter for attachments?

I had thought about it but was concerned as it seems that the little 'teeth' on the mount used to align with the same on the reflector bracket but the Cyoglite bracket kind of just fits inside the mount and can rotate 360 when it shouldn't - so without getting a lock on the 'teeth' I figured the bracket would be susceptible to up/down movement.

I'm guessing the way you've done it, it must just be screwed in tight and so no movement?